1. Field of the Invention
The present invention relates to observation probability calculations for voice recognition.
2. Description of the Related Art
The realm of applications using voice recognition is anticipated to extend to most electronic products normally used in our daily lives. IBM, which was one of the first to propose a technique for utilizing voice recognition, proved the efficiency of a hidden Markov model by applying a hidden Markov model algorithm to voice recognition, as described in U.S. Pat. No. 5,636,291.
The '291 patent discloses a character recognition system applying a hidden Markov model algorithm. The '291 patent organizes the hidden Markov model algorithm into a program implemented by a general-purpose processor.
The voice recognition system disclosed in the '291 patent roughly includes three parts: a pre-processor, a front-end part, and a modeling part. In the pre-processor, the lexemes of all characters of interest are identified. In the front-end part, feature values or parameters, which are comparative, are extracted from recognized lexemes. In the modeling part, a training phase is performed in order to generate a model. The model is used as a standard for precise judgment on the recognized character, based on the extracted feature values or parameters. In addition, based on the recognized lexemes, the modeling part determines which character among pre-assigned characters should be selected as a recognized character.
IBM has also published a voice recognition system and method using a widely-used hidden Markov model algorithm. U.S. Pat. No. 5,799,278 discloses a voice recognition system and method in which isolated voiced words are recognized using a hidden Markov model algorithm. The voice recognition system and method in the '278 patent is trained to recognize phonetically dissimilar words, and is suitable for recognizing a substantial number of words.
The voice recognition systems described above require substantial processing time to execute calculations necessary for voice recognition. An observation probability calculation used in these systems occupy about 62% of the total number of calculations required by a voice recognition device using a hidden Markov model algorithm.